G.O.P. Senators’ Letter to Iran About Nuclear Deal Angers White House

WASHINGTON — The fractious debate over a possible nuclear deal with Iran escalated on Monday as 47 Republican senators warned Iran about making an agreement with President Obama, and the White House accused them of undercutting foreign policy.

In a rare direct congressional intervention into diplomatic negotiations, the Republicans signed an open letter addressed to “leaders of the Islamic Republic of Iran” declaring that any agreement without legislative approval could be reversed by the next president “with the stroke of a pen.”

The letter appeared aimed at unraveling a framework agreement even as negotiators grew close to reaching it. Mr. Obama, working with leaders of five other world powers, argues that the pact would be the best way to keep Iran from obtaining a nuclear bomb. But critics from both parties say that such a deal would be a dangerous charade that would leave Iran with the opportunity to eventually build weapons that could be used against Israel or other foes.

While the possible agreement has drawn bipartisan criticism, the letter, signed only by Republicans, underscored the increasingly party-line flavor of the clash. Just last week, the Republican House speaker, John A. Boehner, gave Prime Minister Benjamin Netanyahu of Israel the platform of a joint meeting of Congress to denounce the developing deal, and Senate Republicans briefly tried to advance legislation aimed at forcing Mr. Obama to submit it to Congress, alienating Democratic allies.

The letter came as Secretary of State John Kerry’s office announced that he would return to Switzerland on Sunday in hopes of completing the framework agreement before an end-of-March deadline. Under the terms being discussed, Iran would pare back its nuclear program enough so that it would be unable to produce enough fuel for a bomb in less than a year if it tried to break out of the agreement. The pact would last at least 10 years; in exchange the world powers would lift sanctions.

Whether the Republican letter might undercut Iran’s willingness to strike a deal was not clear. Iran reacted with scorn. “In our view, this letter has no legal value and is mostly a propaganda ploy,” Mohammad Javad Zarif, Iran’s foreign minister, said in a statement. “It is very interesting that while negotiations are still in progress and while no agreement has been reached, some political pressure groups are so afraid even of the prospect of an agreement that they resort to unconventional methods, unprecedented in diplomatic history.”

A senior American official said the letter probably would not stop an agreement from being reached, but could make it harder to blame Iran if the talks fail. “The problem is if there is not an agreement, the perception of who is at fault is critically important to our ability to maintain pressure, and this type of thing would likely be used by the Iranians in that scenario,” said the official, who spoke anonymously to discuss the negotiations.

The White House and congressional Democrats expressed outrage, calling the letter an unprecedented violation of the tradition of leaving politics at the water’s edge. Republicans said that by styling it as an “open letter,” it was akin to a statement, not an overt intervention in the talks.

“It’s somewhat ironic to see some members of Congress wanting to make common cause with the hard-liners in Iran,” Mr. Obama told reporters. “It’s an unusual coalition.”

Other Democrats were sharper. Josh Earnest, the White House press secretary, called it “just the latest in an ongoing strategy, a partisan strategy, to undermine the president’s ability to conduct foreign policy.” Senator Harry M. Reid of Nevada, the Democratic minority leader, said the “Republicans are undermining our commander in chief while empowering the ayatollahs.”

The letter, drafted by Senator Tom Cotton, a freshman from Arkansas, and signed by all but seven members of the Senate Republican majority, warned Iran that a deal with Mr. Obama might not stick. “The next president could revoke such an executive agreement with the stroke of a pen, and future Congresses could modify the terms of the agreement at any time,” said the letter, whose existence was reported earlier by Bloomberg News.

Mr. Cotton said he drafted the letter because Iran’s leaders might not understand America’s constitutional system. He also said the terms of the emerging deal were dangerous because they would not be permanent and would leave Iran with nuclear infrastructure. He noted that four Republican senators who may run for president signed his letter and added that he tried without success to get Democrats to sign.

“The only thing unprecedented is an American president negotiating a nuclear deal with the world’s leading state sponsor of terrorism without submitting it to Congress,” he said on CNN.

The letter revived an old debate about what role Congress should have in diplomacy.

Jim Wright, the Democratic House speaker during Ronald Reagan’s presidency, was accused of interfering when he met with opposing leaders in Nicaragua’s contra war. Three House Democrats went to Iraq in 2002 before President George W. Bush’s invasion to try to head off war. And Nancy Pelosi, the House Democratic leader, went to Syria in 2007 to meet with President Bashar al-Assad against the wishes of the Bush administration, which was trying to isolate him.

An agreement with Iran would not require immediate congressional action because Mr. Obama has the power to lift sanctions he imposed under his executive authority and to suspend others imposed by Congress. But permanently lifting those imposed by Congress, as Iran has sought, would eventually require a vote.

Rather than wait, Republicans, joined by several Democrats, drafted legislation aimed at forcing Mr. Obama to submit the agreement to Congress. But when Senator Mitch McConnell of Kentucky, the Republican majority leader, moved to advance that legislation for a vote, Democrats who support it balked at taking action before the talks with Iran concluded. Mr. McConnell backed off, but the bill may be revived if a deal is reached.

Among the Republicans who declined to sign Mr. Cotton’s letter was Senator Bob Corker of Tennessee, the Foreign Relations Committee chairman, who has been working with Democrats on Iran legislation. “We’ve got a bipartisan effort that’s underway that has a chance of being successful, and while I understand all kinds of people want to weigh in,” he said, he concluded that it would not “be helpful in that effort for me to be involved in it.”

Some Democrats, like Representative Brad Sherman of California, said the letter and other moves risked making it a party-line issue, in which case it would be impossible to muster a two-thirds vote to override a presidential veto. “The number of Democrats not willing to follow the president’s lead is reduced when it becomes a personal or political issue,” he said.

Correction:

A previous version of this article misstated the given name of the senator who drafted the letter from American lawmakers to Iranian leaders. He is Tom Cotton, not Tim Cotton.

Jennifer Steinhauer and Ashley Parker contributed reporting.

A version of this article appears in print on , on Page A1 of the New York edition with the headline: G.O.P. Senators Write to Tehran on Nuclear Pact. Order Reprints | Today’s Paper | Subscribe